Tuning indicator



Feb. 10, 1942. K. EMDE I 2,272,660

. TUNING INDICATOR Filed Feb. 24, 1941 2 Sheets-Sheet 1 BY m): made Feb. 10, 1942. K. EMDE 2,272,660

TUNING INDICATOR Filed Feb. 24, 1941 2 Sheets-Sheet 2 INVENTOR.

Patented Feb. 10, 1942 TUNING INDICATOR Kurt Emde, Itasca, Ill., assignor to Zenith Radio Corporation, Chicago, 111., a corporation of Illinois ApplicationFebruary 24, 1941, Serial No. 380,339

Claims.

This invention relates to tuning indicators, and more particularly to tuning indicators for radio receiving apparatus employing manually adjustable tuning means and a loud speaker.

The principal objects of the invention are to provide a simple and eiiicient construction of the tuning indicator mechanism; to so arrange it as to render it easily accessible for inspection and adjustment; to arrange for a highly desirable location of the speaker within the casing of the apparatus for acoustic'efiects; to provide a conveniently placed, easily readable, large-scale tuning dial; to locate the tuning indicator with respect to the loud speaker so as to considerably reduce the space required therefor within the casing of the apparatus and so that the tuning dial and speaker openings may be associated in thefront of the casing of the apparatus to economizespace therein, whereby the apparatus maybe more compactly arranged and enclosed, if desired, and whereby the efficiency of both the tuning indicator and the loud speaker may be improved; and to arrange for an improved symmetrical and artistic design of the radio cabinet or casing. These and other objects of the invention and advantages of theconstruction will appear from the following description.

In the drawings, I

Figure 1 is a front elevational view' of a radio receiving set embodying my improved tuning indicator, illustrating the advantageous arrangement of the tuning dial and speaker openings in the front of the casing of a small table model receiver and indicating the relative arrangement of the principal parts of my device with respect theretoby dotted lines;

Figure 2 is a fragmentary, horizontal sectional view, upon a slightly enlarged scale, taken upon the line 2-2 of Figure 1;

Figure 3 is a front, elevational view, partly broken away, taken upon the line 33 of Figure 2, illustrating the arrangement of my tuning indicator with respect to the loud speaker; and

Figure 4 is a fragmentary, vertical sectional view, also upon a slightly enlarged scale, taken upon the line 4-4 of Figure 1, further illustrating the compact arrangement of my tuning indicator with respect to the loud speaker and with respect to the casing of the receiver, the convenient arrangement of the tuning dial and pointer to provide an easily readable tuning scale, and the economy in space required in the front of the casing for the tuning dial and speaker openings.

The particular design of the casing herein shown is not a part of this invention, but it embodies certain features of casing construction which are and which I shall describe and claim. It is to be understood that, while the invention isherein illustrated as applied to a small radio receiving set, known as a table model, it is not in any sense limited thereto. It may be just as well and advantageously applied to larger radio receiving sets, known as floor or console models, and it is particularly suitable for use with tunable radio apparatus which may be associated and encased with other apparatus, such as, for example, radio-talking-machine combinations and radio-television receiving sets.

In the designing and construction of radio receiving sets, it has been the usual practice to arrange the tuning indicator and the loud speaker in eachset a considerable distance apart and to employ entirely separate openings therefor in the casing of the set. In the floor or console models, the tuning indicator is generally located, for obvious reasons, in the upper portion of the cabinet, and the speaker in the lower portion thereof, while, in the smaller or table models, the tuning indicator and the loud speaker are usually arranged back of separate openings located near the opposite ends of the front of the casing. It has been realized that neither of these arrangements of the speaker affords the most desirable acoustic effects. In the console models, the loud speaker should be a considerable distance from'the floor of the room in which the receiver is used, preferably on a level with the ears of the listener, and in the table models, the speaker should be as evenly spaced as possible from the walls of the small casing, preferably in the middle thereof, to obtain the best results.

Aside from arranging for better placement of 'the speaker, various constructions have been devised which propose space economy by arranging the tuning indicator within the hollow of the speaker-cone and positioning the indicator-dial so that it occupies or may be viewed through the speaker opening in the casing, but, so far as I am aware, no satisfactory arrangement of this character has been adopted and used. Popular demand requires a full-view tuning indicator dial sufiiciently large and clearly defined to be satisfactorily readable, regardless of the size of the receiving set and regardless of the size of the loud speaker, and it has been foundthat such a dial may not be positioned to occupy or be viewed through the speaker opening in the casing without materially interfering with the speaker output, especially where a small speaker indicator pointer. member 8 or the grille 4 is paralle'lled by the 180- and a correspondingly small speaker opening are employed.

In the arrangement herein provided, it will be observed that the speaker is centrally positioned in the casing; that the speaker opening is in the form of a circular grille, the diameter of which is equal to that of the speaker-cone; and that the tuning dial is arranged closely above and around the entire upper half of the rim of the grille, thereby providing, without interfering with the output of the speaker, a conveniently positioned, easily readable, semi-circular scale, the division markings or graduations of which may be satisfactorily spaced to provide for accurate tuning adjustments.

Referring, first, to Figure l of the drawings, l indicates the outer casing of a small table model radio receiving set; 2, the knob for manually operating the usual or any desired form of oiland-on switch and volume control; 3 the knob for manually operating the tuning means and tuning indicator to be presently described; '4, the circular speaker grille; 5, the opening in the easmg I through which the indicator dial and pointer are viewable; 6, the indicator dial; and I, the

The upper semi-circular rimdeg'ree tuning scale 9 which is traversed by the pointer l. Attention is directed 'to the central an'd'symmetrical arrangement 'of these parts in thefr'ont'of the casing and to the large speaker opening and tuning scale provided by such arrange'ment.

tidally arranged-bafile-plate "l9 completely covers .1

opening?) in casing l (see Figures 2 and) and is formed with a downwardlyprojecting bib which extends around and closely 'back of 'the lower portion of speaker grille-4. A circular recess 2! is formed in bafile-plate I 9 and the back of' this recess is out away-to leave a circular rim 22 and-four radial spider-arms'2'3 joined at the center of the recess and supporting a stud 24. Baffie-plate I9 is secured in position by's'crews 25 passed through the rim of bell-frame l 1, the rim- 'ring 260i cone l8, and the'circularrimZZ' of recess-'Zl.

Tuning scale 9 is arranged upon the "face of baffle-plate I9 as a semicircle scribed from stud 24. As herein shown, the scale9 is displayed upon a card which is held in position upon the face of bafile-plate l9 by meansof rivets 21, but it is to be understood that this arrangement is illustrative only and maybe varied in many ways without departing from the spirit and scope of my invention. The scale may-be etched upon, pressed in or perforated through the baffie-plate, if desired, or the card may be of translucent material and illuminated in various well-known ways, the important point being that it should be accurately arranged with relation to stud 24, so that itmay'be properly traversed bypointer whichis pivotally supported upon the stud. It will be noted that the axis of stud 24 is coincident with that of the circularspeaker' grille l,-and that The loud speaker I l is secured upon the semicircular tuning scale 9 parallels the semicircular rim of the upper half of said grille.

Indicator pointer l is fixed upon the hub 2'8 01. a spoked and grooved pulley 29, which hub is rotatably mounted upon stud 24 and retained thereupon by means of a spring-clip removably snapped into an annular groove (not shown) in the forward end-part of the stud. A second grooved pulley 3|, similar in size to pulley 29, is fixed upon the rotatable shaft 32 of the variable condenser l3, the rotor and stator plates of which are indicated at 33 and 34, respectively, in Figure 2. A short shaft 35 is rotatably supported in any suitable manner upon or within chassis Ill to project forwardly from the front wall thereof through the front of the casing I, and knob 3 is fixed upon the forward end-part of the shaft whereby it may be manually rotated. Shaft 35 is provided with an annular groove 36, which is in tractive alignment with pulleys 29 and 3i, and a cord belt 31 connects the two said pulleys with each other and with the shaft. As shown in Figures 2 and 3, the lower reach of belt 31 extends from pulley ill to pul1ey'29 through opening 38 in the cylindrical wall of recess 2!, the upper reach is brought down through openmesa and'given a turn or two around shaft 35 and thence' back to pulley 3 I, the ends of the belt being joined together by a spiral takeup spring 39.

The single-belt operation of the rotor of the variable condenser'l3 and of the indicator pointer l by the turning of knob 3 is too obvious to require description, but it may be noted that, since pulleys -25] and '3! are of the same size, adjustments of the rotor-plates 33 of the lilo-degree variable condenser l3 will "be correspondinglyindicat'ed by the pointer l uponthe -degree tuningscale '9, and the small diameter of shaft 35, as compared with the diametersof pulleys 29 and ill, will provide what is known as a vernier adjustmen't of the tuning means and thetuning indicator.

In the claims the term speaker grille is not to be understood as limited to the particular form of speaker opening herein shown, but is to be broadly construed as including any construction, method, or material used for disguising-or covering speaker openings and concealing parts otherwise open to view.

I claim:

1. In tunable radio apparatus, a casing,a wall comprised in'saidcasing provided'with a speaker grille and an adjoining tuning indicator View opening, a chassis within said casing, a speaker fixed upon said chassis directly back of the speaker grille insaidwall, a'tuning scale supported upon said'chassis in position'to be viewed through the tuning indicatorview'opening in said wall, movable indicating 'means mounted upon said chassis in front of said'speaker and extending to'traverse said scale upon movement thereof, said indicating means "being partially concealed by the speakerjgrille in saidwall and partially exposed to be viewable with .said scale through the tuning indicator View opening in saidfwall. tuningmeans fixed upon said chassis apart from said speaker, "and manually adjustable means operatively connected with said tuning'means and with said indicating means acting upon adjustment thereof to effect the adjustment of said tuning means and indicate'such adjustment by the positioningof said indicating means with respect to saidtuningscale.

l 2. In tunable radio apparatus, a casing, a wall being coincident with the axis of the circular speaker grille in said wall, an indicator pointer pivotally mounted upon said chassis in front of said speaker, the pivotal axis of said pointer being coincident with the axis of the circular speaker grille in said wall and the free end of said pointer traversing said semi-circular tuning scale, and adjustable tuning means fixed upon said chassis apart from said speaker and said pointer and operatively connected with said pointer.

3. In tunable radio apparatus, a chassis, a speaker and tuning means independently supported upon said chassis, a speaker-cone and a bell-frame comprised in said speaker, said bellframe having a circular rim by which the outer rim of said speaker-cone is supported, a bafileplate having a circular speaker opening therein and secured about said opening to the rim of said bell-frame, an arm extending from the rim to the center of said opening, a stud fixed upon said arm in the center of said opening, a semicircular tuning scale carried by said baflie-plate in position thereupon to constitute said stud as the axis of said scale, a pointer pivotally mounted upon said stud with its free end traversing said scale, and manually adjustable means operatively connected with said tuning means and with said pointer.

4. In tunable radio apparatus, a chassis, a speaker and tuning means independently supported upon said chassis, a bafiie-plate secured to said speaker, a stud fixed upon said bafile-plate in front of said speaker, an arcuate tuning scale carried by said baflle-plate in position to constitute said stud as the axis of said scale, a pointer and a pointer driving pulley fixed with respect to each other and rotatably mounted upon said stud with the free end ofthe pointer traversing said scale, a rotatable adjusting shaft comprised in said tuning means, a driving pulley fixed upon shaft having the same diameter as said pointer driving pulley, a manually adjustable shaft rotatably supported upon said chassis, and means operatively connecting said pulleys with each other and with said shaft.

5. In tunable radio apparatus, a casing, a wall comprised in said casing having a speaker opening and a tuning indicator view opening adjoining each other in the middle of said wall, a chassis within said casing, a speaker fixed upon said chassis directly back of the speaker opening in said wall, a bafile-plate supported closely back of and parallel with said wall, extending beyond the boundaries of the aforesaid openings therein, and having a recess in alignment with the speaker opening in said wall, at the back of which recess said baflie-plate is secured to said speaker, a speaker opening in the back of the recess in said bafiie-plate, a stud supported upon said baflie-plate within the recess therein, an arcuate tuning scale upon said baiile-plate viewable through the view opening in said wall, a pointer rotatably mounted upon said stud with the free end thereof traversing said scale and also viewable through the view opening in said wall, and adjustable tuning means fixed upon said chassis apart from said speaker and said pointer and operatively connected with said pointer.

KURT EMDE. 

